1. Field of the Invention
The present invention relates to a fuel supply system of an outboard motor for supplying a fuel stored in a fuel tank to an intake port of an engine.
2. Description of the Related Art
An outboard motor often used in a small craft is generally provided with a fuel supply system for supplying an intake port of an engine of the outboard motor with a fuel stored in a fuel tank provided on a hull side.
In this fuel supply system, a vapor separator for separating the fuel such as gasoline sucked up from the fuel tank by a low-pressure fuel pump into gas and liquid to release fuel vapor into the atmosphere, a fuel cooler for cooling the fuel having passed through the vapor separator by cooling water (seawater), a high-pressure fuel pump for pumping the fuel having passed through the fuel cooler, a pressure regulator for adjusting pressure of the fuel, an injector for injecting the fuel whose pressure has been adjusted by the pressure regulator to the intake port of the engine, and so on are generally provided.
As a conventional fuel supply system of this type, for example, one in which a high-pressure fuel pump and a pressure regulator are integrally provided in a case of a vapor separator and a water jacket (fuel cooler) for cooling the fuel is also provided in the case of the vapor separator, whereby a fuel system is simplified (for example, refer to Patent Document 1), and the like are publicly known.
However, in this fuel supply system, since the vapor separator and the high-pressure fuel pump are integrally provided, the size of the vapor separator becomes large for an outboard motor, which has a problem of difficulty in making the outboard motor compact.
Therefore, conventionally, a fuel supply system provided with what is called an in-line high-pressure fuel pump connected in the middle of a fuel pipe and also is provided with a vapor separator having an atmosphere open valve for vapor vent (for example, refer to Patent Document 2) and the like have been publicly known.
[Patent Document 1] Japanese Laid-open Patent Publication No. 10-218089
[Patent Document 2] Japanese Laid-open Patent Publication No. 2002-235627
However, generally adopting a structure in which an air vent pipe of the high-pressure fuel pump is returned to the vapor separator, the above-described conventional fuel supply system using the in-line high-pressure fuel pump has a problem that during the operation, the high-pressure fuel pump sucks the fuel inside the vapor separator through the air vent pipe, which is liable to disable the discharge of the air inside the high-pressure fuel pump.
Another problem is that the outboard motor, when detached from a stern board for maintenance or the like, is usually placed on a floor in a lying posture with its vapor separator side down, and at this time, the fuel is liable to leak from the vapor vent pipe or the like of the vapor separator.